currently on Proxmox VE 8.x

I hope you're updating before going live. EOL of 8.x is near.

has anyone configured a similar multi-tenant or hospitality setup on Proxmox where guest and operational traffic share the same physical hardware?

Isn't that the default usecase for any non-small company? I have 6 VLANs at home with their corresponding WiFi APs in place to seperate networks properly.

Most of your questions raise more questions. The access, distribution and core switches are also important, e.g. can a guest access the VLAN of the staff just by knowning the correct VLAN ID? If so, you have a bigger problem that cannot be solved at the PVE level. First, you need to have the network including routers and firewalls to be right for you usecase, PVE is only a small problem down the line.

Normally, your VMs are only accessible in the VLAN they're configured with unless you configure it otherwise. The guests should only access other stuff in other network segments (layer 3) if you have a router configured and it will forward and probably filter the network packages. You will not need to configure VLAN bridges, only if you want to have access to your PVE from other VLANs.